As an Admin, I want to be able to create a rule and immediately see how it impacts my inbox while I am creating the rule, so that I don't need to wait a few days to better understand whether it's behaving in the way that I need it to behave.
Please vote up if this is a pain point that we need to solve for you!
When using Gmail filters, this problem is mostly solved, they allow to search with the same conditions that filters applies.
Hello! Just a suggestion; if you have a rule where the trigger is "inbound message received" (a common trigger), a nifty trick to use to test whether the rule is working is to add an additional trigger of a specific tag being added (that tag itself not being that important, since you're just using it for purposes of testing whether the rule works). Once you've added the application of that tag as a trigger, if you have an email that is an example of one that you'd want your rule to fire on, just apply the tag to that email conversation, and if it meets the conditions, it should fire the rule :)